US 6,137,360 A · Differential amplifier and voltage follower circuit

Abstract

A differential input comparison circuit of an operational amplifier circuit includes first and second input circuits having circuit structures based on a single input direction of an N channel. To a pair of input transistors of the first input circuit, a non-inverting input and an inverting input are directly applied, while to a pair of input transistors of the second input transistor, the inputs are applied via respective level shifters. When the inverting input is lowered, a threshold voltage of the pair of input transistors of the first input circuit cannot be ensured. To prevent this, each level shifter starts operating based on an instruction from a switching circuit to shift respective levels of the inputs to ensure the threshold voltage of the pair of input transistors of the second input circuit. As a result, the operational amplifier circuit can compare the inputs without problems, thereby providing a differential amplifier corresponding to a wide dynamic range which permits input/output operation in an entire range of a power source voltage.

Claims20

Dependent claims

A differential amplifier which compares a non-inverting input to be applied to a non-inverting input terminal with an inverting input to be applied to an inverting input terminal, comprising:

a differential amplifier section for comparing the inverting input and the non-inverting input when an input voltage is in a predetermined operable region;
a plurality of level shifters for shifting respective potentials of the inverting input and the non-inverting input by the same amount in directions so as to allow the input voltage to fall in the operable region when the input voltage is in an inoperable region outside the operable region;
and
a switching circuit for controlling the level shifters so as to make them operable or inoperable based upon whether or not the input voltage is in the operable region.

1 more element

A differential amplifier which compares a non-inverting input to be applied to a non-inverting input terminal with an inverting input to be applied to an inverting input terminal, comprising:

a first input section having a first input transistor for controlling an amount of current flowing there through based on the non-inverting input and a second input transistor for controlling an amount of current flowing therethrough based on the inverting input;
a second input section having third and fourth input transistors for controlling respective amounts of currents flowing therethrough based on the non-inverting input and the inverting input to be applied through said level shifter, said third and fourth input transistors respectively having the same polarities as the first and second input transistors;
an output section for outputting a voltage according to a difference between a sum of currents flowing through said first and third input transistors and a sum of currents flowing through said second and fourth input transistors, and
a plurality of level shifters for shifting respective potentials of the inverting input and the non-inverting input by the same amount in directions so as to increase the currents flowing through the third and fourth input transistors.

1 more element

Dependencies are inferred from the claim text.

Differential amplifier and voltage follower circuit

Life of this patent

Differential amplifier and voltage follower circuit

Life of this patent

Abstract

Claims20